1. Field of Invention
Exemplary embodiments of the present invention relate to a light source unit and a projector. More specifically, exemplary embodiments relate to a light source unit using a solid-state light emitting device.
2. Description of Related Art
A related art light source unit for a projector can use a discharging lamp, such as a metal halide lamp, a xenon lamp, an extra-high voltage mercury lamp, or devices. Such a discharging lamp is high in intensity and efficiency, but requires a high-voltage power supply circuit. The high-voltage power supply circuit is large in size and thus heavy, thereby preventing the projector from being reduced in size. Even more disadvantageous is the fact that the useful life of the discharging lamp is not long enough. Moreover, the discharging lamp has considerable difficulty in quick lighting-up and lighting-off, modulation, and the like. Especially, to turn on the discharge lamp, it takes a long time, such as several minutes, for example.
This is the reason why a light source unit using a solid-state light emitting device may be advantageous. A related art solid-state light emitting device includes a light emitting diode (hereinafter “LED”), which may become advantageous. In addition to a low-output LED for display, a high-output LED for illumination may be used. The LED has characteristics of being ultra-compact and ultra-light, and having a long life. In this sense, the LED is considered suitable for the use with a projector, specifically with a light source unit for a small-sized portable projector.
The LED has other characteristics of, through control of a drive current, without difficulty, quick lighting-up, lighting-off, and modulation (adjustment for the amount of light emission) of the order of a millisecond. By utilizing the high-speed drive of the LED, it becomes possible to sequentially lighten-up, for illumination, the LED for red light beams (hereinafter “Red light beams”), the LED for green light (hereinafter “Green light beams”), and the LED for blue light (hereinafter “Blue light beams”) on a video frame basis, for example. Further, by LED pulsed radiation and light-emitting time integration, there is the prospect of larger output. Another prospect is that, as a result of LED pulsed radiation, a so-called tailing phenomenon can be reduced, causing image afterglow looking as if moving images displayed on a screen have tails.
In a case of using LEDs as a light source of a projector, to ensure the sufficient level of intensity, a large current, of about 1 ampere for every LED, must be supplied. If such a large current is supplied to the LEDs with the above-described high-speed drive, it may generate strong electromagnetic waves from a current line that is provided for current supply to the LEDs. If generated, the resulting electromagnetic waves from the current line are not needed for the projector. If the emitted electromagnetic waves are strong, this may result in malfunctions of the projector and its peripheral equipment, deleterious effects on health, and others. In view of this, it may be advantageous to provide constraints of product electromagnetic compatibility to reduce or prevent generation of any unnecessary electromagnetic waves. A related art technology of reducing such unnecessary electromagnetic waves in light emitting devices is disclosed in JP-A-11-340515.